One limitation of using radiation in the treatment of liver cancers is the inability to deliver a high dose of radiation due to adjacent normal tissues that must be treated in order to ensure target coverage. The radiation treatment margin must account for organ motion due to breathing, which can be significant. By eliminating target motion secondary to breathing, the volume of normal liver irradiated is decreased, allowing a higher dose of radiation to be delivered to liver tumors. Active breathing control (ABC) is a novel method of minimizing target motion due to breathing during radiotherapy. The radiotherapy treatment machine is turned on only during the period when breathing motion is temporarily immobilized. If this approach can be made practical, it will permit less normal tissue to be treated during radiotherapy, which will permit the safe delivery of higher doses of radiation. The primary goal of this research project is to determine the reproducibility of liver immobilization using a controlled breath hold during radiation treatments of liver cancers. Patients of all age, gender, ethnicity and race with hepatic malignancies who are planned to receive radiation therapy in Protocol UMCC 9604 at the University of Michigan are candidates for the present study. Written informed consent for the present study will be obtained for all subjects. Patients will be treated using an ABC apparatus, producing a controlled breath hold of at least 10 seconds, during which the radiation will be delivered. Radio-opaque platinum microcoils will be placed in the liver at the time of hepatic artery catherization (which is required for Protocol UMCC 9604). Daily orthogonal radiographs will be taken prior to each radiation treatment, and three planning CT scans (using ABC) will be obtained to allow measurements of the organ immobilization reproducibility using ABC. Provisions will be made during the planning process to generate a backup plan that can be used if a patient cannot tolerate the ABC apparatus. In addition, the protocol is structured to have a test period for each patient to become familiar with the ABC apparatus prior to being treated with radiation, minimizing the chance of any patient not tolerating the ABC apparatus while receiving radiation. It is anticipated that by using ABC, internal organ motion that occurs during regular breathing will be significantly minimized, allowing less normal tissue to be irradiated and a higher dose of radiation to be delivered to the liver tumor.